#include <stdio.h>
int question18();
int question19();
int main(){
    question19();
    return 0;
}
//求5！
int question18(){
    int i,t;
    t=1;
    i=2;
    while (i<=5)
    {
       t=t*i;
       i++;
    }
    printf("%d\n",t);
    
    return 0;
}
//求多项式1-1/2+1/3-1/4+...+1/99-1/100的值
int question19(){
    int sign=1;
    double deno=2.0,sum=1.0,term;
    while (deno<=100)
    {
        sign=-sign;
        term=sign/deno;
        sum=sum+term;
        deno=deno+1;
    }
    printf("%f\n",sum);
    return 0;
}